Brane-antibrane action from boundary string field theory

In this paper we give the boundary string field theory description of brane -antibrane systems. From the world-sheet action of brane-antibrane systems we obtain the tachyon potential and discuss the tachyon condensation exactl y. We also find the world-volume action including the gauge fields. Moreove r we determine RR-couplings exactly for non-BPS branes and brane-antibranes . These couplings are written by superconnections and correspond to K-1(M) and K-0(M) for the non-BPS branes and brane-antibranes, respectively. We al so show that Myers terms appear if we include the transverse scalars in the boundary sigma model action.